Positive Displacement pumps are widely used in various applications including but not limited to chemical injection and metering systems, where a chemical additive is injected from a storage reservoir into a process. The chemical additive can have a significant role in the process, such that continuously verifying the injection rate and proper operation of the pump is necessary. It is difficult if not impossible to verify if the pump is injecting proper amounts of the chemical by visual inspection only. Conventionally operators verify pump flow-rates by isolating the chemical supply and pumping from a draw down column on the suction side. Some of the malfunctions that affect a pump's flow-rate include, but are not limited to, loss of chemical supply, check-valve malfunction, line blockage, leakages in the diaphragm or in the lines, and loss of actuation.
There are some patents that directly or indirectly endeavour to address this problem: U.S. Pat. No. 4,549,853 (Gasper et al) Positive Displacement Pump Output Monitor; U.S. Pat. No. 5,038,893 (Willner et al) Lubrication Monitoring System; U.S. Pat. No. 5,237,310 (Smith) Pump Monitor; and U.S. Pat. No. 5,315,294 (Toth) Fluid Metering Verification System.